I. Field of the Invention
The present invention relates generally to industrial and commercial adhesives and, more particularly, to a solvent-free, water-based polyurethane latex adhesive of relatively rapid cure that may be used advantageously to adhere a wide variety of types of floor covering materials to a variety of flooring materials. The adhesive is solvent-free and relatively water and solvent resistant after cure and may be cross-linked to provide additional environmental resistance as desired, particularly for outdoor installations.
II. Related Art
Presently, the most prevalent, conventional multi-purpose floor covering adhesive materials include a styrene-butadiene latex (SBR) or an acrylic latex material. Conventional premium grade multi-purpose floor covering adhesives using styrene-butadiene latex (SBR) generally include SBR latex, water, alkali (pH modifiers), Kaolin Clays slurry (fillers), aliphatic resins, naphthanic oil (emulsified), freeze-thaw additives, antimicrobial additives and thickeners. The aliphatic resins and naphthanic process oils require emulsifiers, normally surfactants, such as fatty acid, tall oil or laural sulfate based surfactants. These adhesives have been used for a period of time to successfully attach a variety of materials to a variety of floors.
However, SBR-based conventional multi-purpose floor covering adhesives do have certain drawbacks which limit their desirability. While generally described as multi-purpose, the formulas typically must be modified to accommodate each specific type installation, i.e., each distinct floor covering product to be glued. Conventional SBR adhesives exhibit very poor alkali and moisture resistance, making them unsuitable, for example, for outdoor use. These materials also do not exhibit long-term resistance to plasticizer migration when used, for example, in conjunction with polyvinyl chloride materials with dense vinyl backing. SBR latex adhesives characteristically have poor resistance to soaps, surfactants, and solvents (for example, VM&P naphtha, paint thinners, degreasers, and other cleaning liquids). Furthermore, these adhesive materials include naphthanic oils and/or aliphatic resins which must be emulsified, i.e., these materials must be modified with amounts of surfactants (e.g., fatty acids, tall oils or laural sulfate-based surfactants) to provide adequate compound stability and extended storage or shelf life.
The conventional SBR material itself, also, has definite practical installation limitations. The material requires a rather long (24-72 hours) curing time to develop maximum bond strength. In addition, the curing and set-up cycle are further dramatically affected by cure temperature, relative humidity and other environmental conditions. The volatile solvent materials are also undesirable VOC emitters.
Both water dispersible polyisocyanates (polyurethanes) and methods for obtaining stable aqueous dispersions of hydrophobic polyisocyanates through chemical modifications are known. It is also known to utilize external surfactants or additives or high shear mechanical devices to create relatively stable water dispersions of hydrophobic polyisocyanates. Markusch (U.S. Pat. No. 4,904,522), and Tirpak et al (U.S. Pat. No. 5,185,200) have disclosed the preparation and use of aqueous polyisocyanate emulsions for use as binders in the production of fiberglass mats. Aqueous compositions containing encapsulated polyisocyanate which contains unreacted isocyanate groups also are disclosed by Markusch et al in U.S. Pat. No. 5,191,012). Tirpak et all, in U.S. Pat. No. 5,212,230, create an aqueous polyurea dispersion by reacting a concentrated polyisocyanate and a polyamine in an aqueous medium. Another aqueous binder composition containing a trimerization catalyst that provides aqueous compositions which do not require water to cure and which possess good adhesion properties with regard to glass fibers are illustrated by Metzger et al (U.S. Pat. No. 5,157,074). In addition, dispersions of polyisocyanates in aqueous solutions have been used as sealants to prevent the evaporation of water and thereby to improve the cure and strength of green concrete. The material is applied as a dilute aqueous solution and such a system is shown by Markusch et al (U.S. Pat. No. 5,236,994).
The known art, however, does not suggest the use of water-dispersible polyisocyanate materials as general adhesives; in particular, the art does not suggest that such materials would be of particular value as floor covering adhesives.
It is an object of the present invention to provide a universal, water-based adhesive formulated with a polyisocyanate (polyurethane) latex suitable to adhere many types of materials.
A further object of the invention is to provide a cross-linkable universal, water-based adhesive material suitable for indoor or outdoor use.
Another object of the invention is to provide a cross-linkable universal, water-based, polyurethane latex floor covering adhesive suitable to adhere all types of floor covering materials and suitable for indoor or outdoor use.
Yet another object of the invention is to provide a universal, water-based polyurethane latex floor covering adhesive which is solvent-free and has extremely low VOC emission rendering it environmentally benign for indoor as well as outdoor use.
A still further object of the present invention to provide a universal water-based polyurethane latex floor covering adhesive that can incorporate a wide variety of cross-linking chemical substances which are solvent-free, low VOC emitters.
Yet still another object of the present invention is to provide a water-based universal polyurethane floor covering adhesive that, with cross-linking, is extremely resistant to most common household and industrial solvents and cleaners.
A yet still further object of the invention is to provide a water-based polyurethane floor covering adhesive that is alkali resistant and resistant to plasticizer migration.
Other objects and advantages should become apparent to those skilled in the art upon further consideration of the description and accounts contained in this specification.